This invention relates to textile machines, such as spinning frames (including ring spinning frames), twisters (including single, double, ring and drawing twisters) and the like, wherein a plurality of spindles are driven and rotated by a traveling belt and a balloon of yarn is formed around the yarn package on each associated spindle upon rotation of the spindle, and more particularly to sound reducing devices in these textile machines.
In general, the textile machine of the type described includes a number of sound sources, by which noise of a relatively high sound level is produced during its operation. It is well known that such a noise comprises mainly sound produced by the travel of the belt, sound of the driving contacts between the travelling belt and the spindle wharves, and sound produced in forming the balloons.
In order to reduce the sound level of such a noise produced by the various sound sources, heretofore, several sound reducing arrangements have been proposed. For example, U.S. Pat. No. 3,782,087 discloses a double twister, wherein a sound reducing cover is provided to cover all of the spindle assemblies each comprising a driving section where the spindle wharves are driven by the travelling belt, and a balloon forming section where a balloon of yarn is formed. British patent specificiation No. 1,030,077 shows a double twist frame, wherein only the contact portions between the travelling belt and the spindle wharves are encased in a single sound reducing cover.
Of these exemplified prior sound reducing devices, the former arrangement has such drawbacks that a satisfactory sound reducing effect cannot be expected unless the sound reducing cover is designed to be of a great thickness; and that undesirable yarn waste produced in the balloon forming sections during ballooning accumulates at the contact portions between the travelling belt and the spindle wharves and at the braked portions of the spindles, causing inconvenience to the driving and braking of the spindles. As is understood, these drawbacks result from the fact that both the balloon forming sections and the spindle driving sections are disposed in the common single sound reducing chamber. With the latter arrangement, since the balloon forming sections of the spindle assemblies, which are the source of high sound level noise, are exposed to the atmosphere in which the double twist frame is arranged, it is not satisfactory for reducing the noise produced by the double twist frame in spite of the provision of the sound reducing cover.
It is therefore an object of this invention to eliminate the above mentioned drawbacks peculiar to the prior art sound reducing devices and to provide an improved sound reducing device in a textile machine having a plurality of spindle assemblies, which can satisfactorily reduce a high level of noise mainly comprising sound of the belt travel, sound of the contacts between the travelling belt and each spindle wharves, and sound produced in forming the balloon at each associated spindle assembly and makes it ensure that yarn waste produced during ballooning is prevented from accumulating at the driven portions of the spindle wharves contact with the belt.
It is another object of this invention to provide a sound reducing device in a textile machine having a plurality of spindle assemblies, which can prevent an occurrence of undesirable mutual interferences in air stream, yarn waste, and hot air, which is produced due to the friction at the driven portions of the spindle wharves, between the adjacent spindle assemblies.
According to the art of sound, sounds produced by various sources of noise are called "composite noise" and, in the case where an intensity of particular sound forming a part of the composite noise is to be measured, the residual sound is called "back ground noise." With respect to relationships between the composite noise and the back ground noise, it is generally acknowledged that when the difference in sound-pressure level between them is 3 db the sound-pressure level of the particular sound is that of the composite noise less 3 db; when the difference is within 4.about.5 db the level of the particular sound is less than that of the composite noise by 2 db; when the difference is within 6.about.9 db, the level of the particular sound is less than that of the composite noise by 1 db; and when the difference becomes more than 10 db, the level of the particular sound is substantially identical with that of the composite noise, that is, the back ground noise can be ignored.
The applicants of this invention have found the facts that in the case of the conventional textile machine, such as a double twister without any sound reducing cover, the aforementioned noise consisting of (1) the sound produced by the driving contacts between the travelling belt and the spinning wharves; (2) the sound of the travel of the travelling belt; and (3) the sound produced in the balloon forming sections of the spindle assemblies, where the yarn balloons are formed, is greater in intensity than any other noise by 10 db or more and there is no substantial difference in sound-pressure level between the sound (1) + (2) and the sound (3).